Thread: Thoughts on Slimraw

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  1. #1 Thoughts on Slimraw 
    HI all. Been using my BMCC quite a lot lately and have gotten spoiled with RAW 3:1 out of the Micro. Thinking about Slimraw and have a couple of questions from those of you using it.

    I think I just want to convert footage from RAW to Raw 3:1 to save drive space. Are there any drawbacks. Does it take a lot of time. Do you even keep your original footage. Probably some questions I'm not thinking of right now but imagine you get the drift.

    Appreciate the advice.
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  2. #2  
    Senior Member Zolac's Avatar
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    -Does it take a lot of time?
    This obviously depends on your system specs, however having tested on a variety of systems I will say that for the most part you can expect at LEAST ~realtime performance ( 45 mins of RAW will be 45 mins to convert )
    With a relatively modern system you can do even better, sometimes 2x-4x real-time performance.
    Performance is also very closely attributed to Disk Speed ( both source and target disk), converting footage directly off the SDD with a SATA3 interface or USB 3 definitely helps.
    In summary, speed is very good. So good I honestly don't ever find myself just offloading the footage on its own.
    I will run all my footage through it because I gain all the benefits of extra compression with negligible ( if any! ) penalties in terms of speed. ( that in addition to some other awesome features like 2x downscale and checksums )

    -Do you even keep your original footage?
    I find the Lossy compression sufficient enough that I usually don't need to archive my originals, although this simply comes down to personal preference/workflow.

    It's sort of just become my go to process for archive and offloading my BMCC footage.
    Last edited by Zolac; 11-11-2017 at 03:28 PM.
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  3. #3  
    Are there any drawbacks?

    You mean, besides lowering the quality of your footage? Kind of. Compatibility is reduced as well, on account of Adobe still not having great compressed CinemaDNG support.

    Does it take a while?

    Depends entirely on what you're reading from and what you're writing to. If you're copying from and writing to the same 5400RPM laptop drive then yes, it'll take a while. If you're copying from one RAID0 to another RAID0 then it is pretty fast. Also depends on how much footage you're processing and how good your machine is.

    Do you keep your original footage?

    I don't use lossy compression but I do losslessly compress DNGs from my Bolex all the time. Ideally, I keep two copies of the original DNGs from camera and a single copy of the losslessly compressed versions, and because HDDs are so affordable I tend to just keep stuff around. Unless you're shooting years and years of footage for a doc, I don't really see a need to use lossy re-compression and/or toss my original footage.
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  4. #4  
    Thanks Zolac and Alex. Appreciate the advice.

    For clarification I'm sure like all of you every shoot is a little different. Yesterday I came in with about 120GB's from my Micro camera, which I set at RAW 3:1. I used the micro as a B Cam in about a hour interview as well as lot's of B-roll and roving footage of the event. The BMCC came in at 250GB and was only used as the A Cam in the same interview. I also recorded sound and shot some stills so ended up around 400 GB's. If the BMCC was RAW 3:1 I'd save about 160GB's which would over months save me quite a lot of money.

    I bring the footage initially into Resolve and general go through initial color. It's put on an internal 6G HD spinning at 7200 RPM's. I'm currently using 4GB drives. Once I've input all the files I copy them over to the job file on a RAID 0 drive. That job file is then archived with Chronosync and then synced each day. That Archive drive is duplicated using Chronosync about once a week with the duplicate drive being taken off premise. Once I'm through an initial grade in Resolve I output the files I'll be working with to Pro Res (I've found I like getting right to the final codec though it's not really final yet but honestly doesn't take up much space. Then I sync the audio. In the past I've used PluralEyes for that pretty successfully. I may try to shift that workflow to resolve syncing on Waveform but am not yet sure. From there I usually use Premiere Pro to cut, FX, and all other art and audio from Adobe apps. I have never ever been able to succeed with XML round-tripping a project. I've tried over and over again only to lose days and days of time. My workaround has been as I'm getting towards the end of each project I go through the ProRes files and add a letter or two to the end of the filename then reopen the file in Resolve make the adjustments I want to see and re-save the file with the original filename. Premiere never knows I was even there. The XML workflow would be much nicer but it's never ever worked for me.

    So this all being said the speed bottleneck of all these transfers is the speed of the drives themselves. An empty one starts out writing at about 160,000 Megabits/second but as it get's closer to being full slows down to at least half the speed. I never let drives exceed 85%.

    Alex you mentioned that the file quality is not good enough. Could you elaborate? My goal is simply to bring down the file size from the BMCC so I'm wondering what the drawbacks are.

    Thanks again for your thinking on this. Much appreciated.
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  5. #5  
    Senior Member Dale's Avatar
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    Could be completely wrong, but I thought the BMCC's raw did get compressed a while ago and became the only raw option?

    Also you have to take into account the fact that BMCC's raw is 2.5k rather than fullHD, as well as the bigger sensor size. So even if you have 3:1, you're still pulling in much more data anyway.

    I don't what the compression ratio was, but it was lossless, so no difference in quality/depth. But I swear it gave me an extra 10-15 minutes on a 240gb compared to the original raw option.
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  6. #6  
    Senior Member Frank Glencairn's Avatar
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    I use SlimRaw religiously on pretty much every shot.
    Here is my workflow.

    I shoot in uncompressed raw (Ursa4.6), and use SlimRaw for downloading the files (checksum and all) to my RAID, while compressing them to 3:1 on the fly.
    It takes basically the same amount of time, as just downloading them. Happy camper so far.
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  7. #7  
    Quote Originally Posted by Dale View Post
    Could be completely wrong, but I thought the BMCC's raw did get compressed a while ago and became the only raw option?

    Also you have to take into account the fact that BMCC's raw is 2.5k rather than fullHD, as well as the bigger sensor size. So even if you have 3:1, you're still pulling in much more data anyway.

    I don't what the compression ratio was, but it was lossless, so no difference in quality/depth. But I swear it gave me an extra 10-15 minutes on a 240gb compared to the original raw option.
    Dale you are absolutley correct. They added lossless I think a couple of years back. You also right on the larger resolution which is why I want to use this body more. I think because the BMMCC uses a more advanced processor and the fact that the resolution is smaller they are able to process the data to write RAW 3:1. I've found I like the image that results and really love the savings in data.

    My understanding was that Slimraw could accomplish the same thing in post.

    On personal projects I'd be more apt to reach for the BMCC kit if I knew I wasn't coming home each night with such a huge amount of data to store.

    Thanks for weighing in.
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  8. #8  
    Quote Originally Posted by Frank Glencairn View Post
    I use SlimRaw religiously on pretty much every shot.
    Here is my workflow.

    I shoot in uncompressed raw (Ursa4.6), and use SlimRaw for downloading the files (checksum and all) to my RAID, while compressing them to 3:1 on the fly.
    It takes basically the same amount of time, as just downloading them. Happy camper so far.
    Thanks Frank. That's exactly what I was hoping to hear. It works and is relatively easy.
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  9. #9  
    Quote Originally Posted by Marshall Harrington View Post
    Alex you mentioned that the file quality is not good enough. Could you elaborate? My goal is simply to bring down the file size from the BMCC so I'm wondering what the drawbacks are.
    To be clear, I never said that the quality of 3:1 compression isn't good enough. On the contrary, I think that 3:1 compression is so mild that it's visually indistinguishable from lossless footage in nearly every reasonable scenario. That said, you asked what the tradeoffs were and SlimRAW is discarding data in order to compress those DNGs at a 3:1 ratio. It's worth considering, is all...

    Just to clarify though, I looked at your workflow and I'm not sure why you're choosing to shoot in DNG when a lot of your workflow uses ProRes renders? Honestly, you'd save a lot of time and storage by shooting in ProRes HQ and I bet you wouldn't be able to tell the difference in the final output without an A/B comparison.

    Quote Originally Posted by Frank Glencairn View Post
    I shoot in uncompressed raw (Ursa4.6), and use SlimRaw for downloading the files (checksum and all) to my RAID
    I know you probably know this Frank, but I just want to reiterate for everyone reading this thread that you should not be using SlimRAW to back up your footage. Although SlimRAW does have a checksum function (CRC32), its purpose is only to ensure that both destinations are identical to each other rather than ensuring that both destinations are identical to their source. Obviously, if you're recompressing DNGs there is no way to confirm that your copies are 100% viable.

    If your footage is mission critical then the responsible thing to do is to create multiple copies of your camera original files with a backup utility that supports checksum verification (SilverStack, ShotPut Pro, Hedge, etc.). SlimRAW is an amazing utility that basically takes my Bolex D16 from being a fun trinket to useable camera, but there is no substitute for best practices when it comes to your footage.
    Last edited by Alex.Mitchell; 11-14-2017 at 12:01 AM.
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  10. #10  
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    @Marshall:
    With the BMCC slimRAW users usually use 3:1 or VBR HQ compression. I know some use 4:1. A 4:1 BMCC file has approximately the same amount of color information as a 3:1 file from the Micro. I usually recommend VBR HQ and 3:1 for this particular camera model (I am picky). You may find this write-up on the different compression modes helpful: http://www.slimraw.com/article-cdngmodes.html

    @Alex:
    It is worth mentioning that checksum verification is by its very nature a destination verification procedure: it ensures that something is identical to something else in RAM. To clear it up, this is what slimRAW's checksum verification ensures: that the output is correctly written out. The destinations being identical to each other is only a consequence of them being identical to their master image in RAM after compression, which is the primary goal. Now, if you want to confirm that the source RAM image is (very likely) the same as the source file, you need to read the source multiple times, there is no other way around this. From the backup software you mention, only one does this by default, and one doesn't have the ability at all.
    (The source verification option is coming in slimRAW 1.9, btw, I know you've been waiting for it ).
    Last edited by cpc; 11-14-2017 at 05:11 AM.
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